The theoretical yield of a reaction is the amount of a product produced if all of the reactant is consumed in the reaction or the conversion is 100%. We determine this value by using the initial amount of the reactant and the relation from the chemical reaction. We do as follows:
91.2 g C6H6 (1 mol C6H6 / 78.12 g C6H6) (1 mol C6H5Cl / 1 mol C6H6) ( 112.56 g / 1 mol ) = 131.41 g C6H5Cl